1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device.
2. Description of the Related Art
To form a via hole reaching a copper interconnection, in an interlayer insulating film, dry etching is normally performed using a fluorocarbon family gas. However, the dry etching with the fluorocarbon family gas may result in fluorine remaining on a surface of the copper interconnection. The remaining fluorine may then react with moisture in the air, causing copper corrosion. Accordingly, after the via hole is formed and before the copper interconnection is exposed to the air, the fluorine remaining on the surface of the copper interconnection needs to be removed. If an organic insulating film contained in the interlayer insulating film can be etched simultaneously with the removal of the fluorine, the removal of the fluorine and the formation of an interconnection trench based on the etching of the organic insulating film can be performed during the same step. This allows a manufacturing process to be simplified.
One method for removing the fluorine remaining on the surface of the copper interconnection is a plasma treatment using a mixed gas of a nitrogen gas (N2 gas) and a hydrogen gas (H2 gas) (see Jpn. Pat. Appln. KOKAI Publication No. 2004-247675). However, the plasma treatment using the N2/H2 mixed gas exhibits a high fluorine removal efficiency but offers a low etching rate for the organic insulating film contained in the interlayer insulating film. Consequently, the efficient etching of the organic insulating film is prevented by an attempt to perform, during the same step, the removal of the fluorine and the formation of an interconnection trench based on the etching of the organic insulating film.
Thus, it is conventionally difficult to efficiently perform, during the same step, the removal of the fluorine remaining on the surface of the copper interconnection and the etching of the organic insulating film.